Two fixed-beams TX-diversity

ABSTRACT

A solution is disclosed for minimizing the amount of hardware and hardware accuracy requirements to simultaneously give the feature of both cell and narrow beams transmission, while enabling methods for capacity/coverage increase. The main property utilized by the present invention for maintaining cell-coverage pattern control, when radiating information in two simultaneous beams, is to use orthogonal polarization states for the two beams. The two orthogonal polarization states may for instance constitute linear polarization slanted at +45° and −45°, respectively. The dedicated broadcast transmission needs to be conveyed defining the total cell coverage area. The total cell coverage area is matched by the coverage of the two fixed narrow-beams. The broadcast signal transmission is divided into two signal streams/paths, one for each of the two fixed narrow-beams (no coherency requirements existing between the two parallel signal streams/paths). The two broadcast signal streams/paths are combined by means of combiner units with the dedicated combined signals from all fixed narrow-beam selected users in each of the two branches. The signals to the two antennas are then transmitted having an orthogonal polarization.

This application is the US national phase of international applicationPCT/SE02/01983, filed in English on 1 Nov. 2002, which designated theUS. PCT/SE02/01983 claims priority to SE Application No. 0104012-0 filed29 Nov. 2001. The entire contents of these applications are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a method and an apparatus forsimultaneous transmitting diversity signals into a cell of a cellularsystem having narrow beams utilizing non-coherent signal paths.

BACKGROUND

Up to now cellular systems have base stations using omni-radiatingantennas or antennas radiating in a sector (typically 120° coverage persector). The antennas cover the whole cell and no knowledge of theposition of the mobiles is used.

To increase the coverage and capacity of future systems, large effortshave been put into development of transmit diversity (TX-div)schemes/systems using multiple antenna units. TX-div utilizes multiplesignal source generation to be transmitted via more-or-less independent(non-correlated) propagation channels to the receiver. The aim is toimprove the reception of the received total signal quality. This iscommonly obtained through coherent combining of the several sourcesignals.

Different TX-div methods/schemes commonly put different hardware (HW)requirements on the radiated signals and their relative behavior. Theserequirements can usually be associated to the relative time, phaseand/or amplitude of the radiated signals.

Another method to create capacity/coverage increase in conventionalcellular systems, is to use adaptive antenna arrays at the Radio BaseStation (RBS).

The narrow-beams created by beam forming in the adaptive antenna systemcan be used to increase the coverage by directivity and to reduce theinterference in both the uplink and the downlink. Thus, the idea is toavoid distributed energy which no one can make use of, i.e. minimizingthe interference in the system. In the cellular systems both broadcastinformation (i.e. information addressed to all users in the coveragearea) and dedicated information (i.e. information to a specific mobileterminal) are transmitted simultaneously from an RBS.

Simultaneous transmission in several beams requires coherent signalpaths from the creation of the signal up to the antenna, includingfeeder cable coherency or by additional signal and antenna hardware. Thesignal coherency may set a number of requirements on the implementedsystem hardware, not necessarily the same hardware requirements as forthe TX-div.

Increasing the coverage and capacity through TX-div schemes involvesmultiple signal source generation transmitted via in principlenon-correlated propagation channels to the receiver. To achieve this,multiple antenna units are used. The most common configuration to beproposed is a set-up having two identical antennas separated by adistance sufficiently large. The two antennas illuminate a coveragearea, which in principle is the same for both antennas, see for instanceFIG. 1.

Different methods can be used to support the identification and/orcombination of the source signals, e.g. delay diversity, frequencydiversity, polarization diversity, different identifier (code) forsignal acquisition and combination, feedback correction (i.e. receivermeasurements communicated back to the transceiver for correction oftransmitted signals).

In all common cellular systems (GSM, Global System for Mobiletelecommunications; PDC Pacific Digital Cellular system; TDMA-IS136 TimeDivision Multiple Access; EDGE Enhanced Data rates for Global Evolution;UMTS Universal Mobile Telecommunications System) the TX-div isproposed/used in the downlink, i.e. multiple source signals from thebase station are transmitted towards the mobile receiver.

For example in the Universal Mobile Telecommunications System FrequencyDivision Duplex (UMTS-FDD) (WCDMA, Wideband Code Division MultipleAccess) there are several TX-div modes defined in the standard [1] asthe open-loop Space Time Transmit Diversity (STTD), closed-loop modeland mode2. The mentioned WCDMA TX-div modes above are regardingconfigurations and schemes utilizing two TX-div branches. In the futureit may be standardized even schemes for higher order number of TX-divbranches.

In these schemes, there are rather strict requirements on the relativephase, amplitude and/or time accuracy between the signal paths in theTX-div transmission branches

To utilize the potential performance (capacity/coverage) advantages ofmulti-beam, especially for two fixed-beams as a TX-div solution,requires simultaneous transmission for both cell and narrow beamcoverage. A number of issues that must be fulfilled for a cost-effectivesystem have been identified:

Less or equal amount of hardware resources should be required as for aconventional TX-div system with two sector coverage antennas.Specifically, for UMTS-FDD (WCDMA), there shall be no change of RBS(Node B) hardware configuration for TX-div, except antenna hardware andmounting. Requirements on components and/or subsystems must not beincreased.

In order not to introduce additional complexity it is required that noadditional coherency requirements are introduced in the system. Ingeneral, due to vector addition of transmitted signals, simultaneoustransmission in two beams requires coherent signal paths from thecreation of signals up to the antenna, including feeder cable coherency.Otherwise the radiation pattern will be uncontrolled and can havesignificant variations, including possible directions with nulls in theradiation pattern. Such coherent signal paths are very delicate toachieve in an installed product with several years of expected lifetime.That kind of solution will include calibration loops and controlfunctions that are expensive to introduce in the system. The issue is tocreate the coherent antenna system behavior without requiring signalcoherency.

Capacity/Coverage: The solution must not limit the possibility toutilize the full potential of the Two Fixed-Beam TX Diversity system.The potential of such a system is expected to achieve better performancethan a conventional TX-div system.

No standardization changes are desired: One major requirement is that nointeraction with the mobile/terminal is allowed outside the standardprotocol. The solution should be transparent to the system.

SUMMARY

A novel solution is proposed minimizing the amount of hardware andhardware accuracy requirements, which simultaneously gives the featureof both cell and narrow-beams transmission, while enabling methods forcapacity/coverage increase.

The main property utilized for maintaining cell-coverage patterncontrol, when radiating information in two simultaneous beams, is to useorthogonal polarization states for the two beams. The two orthogonalpolarization states may for instance constitute linear polarizationslanted at +45.degree. and −45.degree., respectively.

The dedicated beam transmission, broadcast transmission needs to beconveyed defining the total cell coverage area. The total cell coveragearea is matched by the coverage of the two fixed narrow-beams. Thebroadcast signal transmission is divided into the signal streams/paths,one for each of two fixed narrow-beams (no coherency requirementsexisting between the two parallel signal streams/paths). The twobroadcast signal streams/paths are combined by means of combiner unitswith the dedicated combined signals from all fixed narrow-beam selectedusers in each of the two branches. The signals to the two antennas arethen transmitted having an orthogonal polarization. An alternativesolution is to combine dedicated user signals selected for transmissionover the specific fixed narrow-beam together with an associatedbroadcast signal stream in the same combiner unit.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will be further described by making reference to theattached drawings in which:

FIG. 1 shows a block diagram of a TX-div antenna configuration whereinthe two antennas are separated by a sufficiently large distance andcovering mainly the same area;

FIG. 2 shows a block diagram of multi-beam array with switched beamports;

FIG. 3 illustrates a beam configuration from a conventional beam-formingarray;

FIG. 4 shows a block diagram of multi-beam array with a separatebroadcast antenna system;

FIG. 5 shows a block diagram of the solution with two fixed-beamTX-diversity including resulting overlaying beam patterns according toan example embodiment;

FIG. 6 illustrates a schematic drawing of the two fixed narrow-beampatterns of the solution with two fixed-beam TX diversity;

FIG. 7 is a schematic drawing of the cell coverage beam patternaccording to an example embodiment wherein two time synchronized signalsfeeds the antenna solution giving an undefined polarization state in theregion between the two narrow-beams;

FIG. 8 shows a block diagram of the solution with two fixed-beamTX-diversity according to one alternative example embodiment, withresulting overlaying beam patterns;

FIG. 9 shows a block diagram of the solution with two fixed-beam TX- andRX-diversity according to another alternative example embodiment,utilizing duplex filters;

FIG. 10 shows a block diagram of the solution with two fixed-beam TX-and RX-diversity according to still an alternative example embodiment,without duplex filters; and

FIG. 11 illustrates an illustrative flow diagram of an example method.

DETAILED DESCRIPTION

Hardware requirements on TX-div as described here are limited to twotransmit signal paths/branches, with no need for a separate broadcasttransmission signal path.

The capacity/coverage improvement using adaptive antennas are previouslydescribed in a number of documents [2], [3], [4] referenced below.Without changing the cellular base-station grid including its sectorcoverage layout, the interference level in the system may be reduced(less interference is received and spatial spread out) by utilizingbeam-forming methods with narrow-beams based on knowledge of the actualpositions of the mobiles.

Simultaneous transmission in several beams of present multi-beam basestation, antenna configurations requires coherent signal paths from thesignals creation up to the antenna, including feeder cable coherency.The coherency is required for control of antenna pattern characteristicswhen transmission is directed to more than one beam. This may be solvedby including calibration networks, which keep track of signal paths andof algorithms, which compensate for inaccuracies and variations. Anotheralternative for broadcast transmission is through a separate antennasystem.

In all previously presented solutions the amount of hardware and/orhardware requirements has been increased in order to facilitatetransmission of broadcast information (cell coverage beam).

In FIG. 2 is shown the block diagram for a typical multi-beamconfiguration, with the corresponding beam pattern shown in FIG. 3. Inthis configuration broadcast information is sent through a coherentcombined radiation of signals. The other alternative for broadcasttransmission, through a separate antenna system, with separate feeder isshown in FIG. 4.

Broadcast information is transmitted in two narrow-beams without signalcoherency, simultaneously as transmitting dedicated information onseparate narrow-beams.

The main property utilized for maintaining cell-coverage pattern controlwhen radiating in two beams simultaneously, is to use orthogonalpolarization orientation for the two beams. The two orthogonalpolarization directions can e.g. be linear polarization slanted.+−.45.degree. An example of a block diagram principally describing anexample transmitter for two beams is shown in FIG. 5, and an example ofthe corresponding beam patterns for the two narrow-beams is shown inFIG. 6.

For two time-synchronized signals, there may be a shift of signalpolarization direction in the overlapping region between the two beams,but signal level will remain at an expected level as shown schematicallyin FIG. 7. Accordingly there does not exist any coherency requirementbetween different polarization planes.

For two-signal time unsynchronized, the polarization of each set ofbeams will remain, and the signals from the two beams will beindependent in the two original beam patterns.

As a consequence, in the overlapping beam region, independent of timeand phase relation, the transmitted signal in the two beams will beadded in the receiver creating the cell-coverage pattern.

Referring to FIG. 5, signaling to a specific user #k is selected to betransmitted via a dedicated channel over two dedicated narrow-beams (#1or #2). The selection of beams (by a beam selector shown in 5) is basedupon directional/angular/spatial information, which may be obtained fromjoint uplink transmission related to the specific user #k. Based uponthis narrow-beam selection for the specific user #k at a time instant(adaptively updated decision), the signal to be transmitted isdirected/switched to a combining unit. In this unit all active dedicatedusers selected for transmission over the specific narrow-beam (i.e., #1or #2) are combined. The transmission of the combined signals from allnarrow-beam #1 selected users are simultaneous with the transmission ofthe combined signals from all narrow-beam #2 selected users, i.e. bothnarrow-beams are active with different users signal at each time.

In parallel to the described dedicated beam transmission, broadcasttrans-mission needs to be conveyed defining the total cell coveragearea. The total cell coverage area shall be matched by the coverage ofthe two fixed narrow-beams. The broadcast signal transmission is dividedinto two signal streams/paths, one for each of the two narrow-beams (nocoherency requirements exists between the two parallel signalstreams/paths). The two broadcast signal streams/paths are combined incombining units with the dedicated combined signals from all narrow-beamselected users in each of the two branches. The signals to the twoantennas are then transmitted with in principal orthogonal polarization.An alternative solution is to combine dedicated users signals selectedfor transmission over the specific narrow-beam (#1 or #2) together withthe associated broadcast signal stream in the same combiner unit, seeFIG. 8.

The above described switching and combination of the broadcast and alldedicated signals are preferable handled in base-band processing. Thisis of course possible to do either in analog or digital domain orcombinations thereof. However, the switching and combining is preferablehandled in the digital domain. Alternatively, all or part of theswitching and combining of the described signals can be performed at IF(intermediate frequency) or RF (radio frequency).

When and if RF components are introduced, a number of different poweramplifiers (PA) positions are possible. After combination of severalsignals, linearity requirements is increased on the power amplifiers andhandled by so called Multi-Carrier Power Amplifiers (MCPA). Beforecombination, so-called Single-Carrier Power Amplifiers (SCPA) aresufficient as the linearity requirements are less severe. The number ofamplifiers needed is reduced for each level of combination of signals.But, of course the total requirement of output power is increased peramplifier for each level of signal combination.

Due to the losses in the switching and combining components it can beadvantageous and preferred to locate the PA's as late as possible in thetransmit chain. As example, possible MCPA locations are indicated inFIG. 5 and in FIG. 8.

It is essential that the system can make transmit beam selections basedupon directional/angular/spatial information. One alternative is to getthis information from the associated uplink transmission from the user.

For such an alternative, one example is to require overlaid beams (samebeam direction) in both uplink and downlink to cover the same area. Theinnovation presented here may have orthogonal oriented polarizationplanes (e.g. linear polarization slanted .+−.45.degree.) for uplink anddownlink in each angular beam direction, as described in, but inprinciple the proposed transmission solution does not impact theselection of receiver method.

The main objective is to support/enable enhanced capacity/coverage forthe downlink transmission direction. However, from a system perspectiveit is in principal essential to have capacity/coverage link balancebetween the two communication directions. If no link balance can besupported, one link will limit the capacity/coverage of the system andavailable performance for the non-limiting link can not be utilized.Implementing the proposed solution for the downlink, it may be importantto also improve the uplink such that the enhanced capacity in thedownlink can be utilized.

A preferred configuration, to improve the uplink communication link, isto use the same dedicated beams in up-link and downlink. The uplink anddownlink signals are separated in duplex filters attached to each of thededicated beam feeders, according to FIG. 9. The feeder cables for eachbeam carries both the uplink and downlink information. With thissolution, two uplink signals are received from the two beam directionsand diversity reception can be made. FIG. 9 further shows that the twouplink signals are applied to a receiver which is connected to a beamselector. The beam selector uses the directional/angular/spatialinformation obtained from the two uplink signals to make beamselections. To this end, beam selector is connected to the switches.

An alternative configuration is to use overlaid beams in both up- anddown-link that covers the same area, but have orthogonal orientedpolarization planes (e.g. linear polarization slanted ±45°). With thissolution the dedicated beam direction #1 have one polarizationorientation in uplink (e.g. −45°) and the orthogonal orientedpolarization in downlink (e.g. +45°). For beam direction #2 the oppositepolarization directions are used, according to FIG. 10. In this solutionseparate feeder cables carries the up-link and downlink information.

In both discussed configurations, two uplink signals are received fromthe two beam directions and diversity reception can be made. The uplinksolutions exemplified in FIG. 9 and FIG. 10, can be used with anydownlink solution, not limited to the one shown in the Figures.

In FIG. 11 is presented a flow diagram, which generally illustrates theproposed method in accordance with an example embodiment. Five acts 1 to5 are applied for transmitting signals into a dedicated cell and at thesame time producing a broadcast signal defining total cell coverage of acellular system and still utilizing narrow-beams and non-coherent signalpaths.

Assuming antennas with the same height, the proposed uplink diversityconfiguration will have a directivity gain of approximately 3 dBcompared to a conventional sector coverage system. This additionaldirectivity gain is due to that the beam covers approximately half theazimuth angular region (half the cell).

In a noise-limited environment, the proposed uplink diversityconfiguration will also give diversity gain from the 2 antenna branches.When the channel angular spread is rich, higher diversity can beexpected. In total, the directivity and diversity gains of the proposedconfiguration is expected to outperform traditional and conventionalsector coverage space or polarization diversity configuration. This isespecially true for broadband type of systems like WCDMA.

Further, in an interference-limited environment, the proposed uplinkdiversity configuration will also give additional interferencesuppression of approximately 3 dB in an environment with uniformlyspread users. This additional interference suppression is due to thatthe beam cover approximately half the azimuth angular region (antennapattern suppresses users from half the cell). In CDMA based systems, thegain from the interference suppression is especially valuable, sinceusers using the same frequency channel/spectrum are co-located in thesame cell.

In the proposed solutions, downlink beams directed at different azimuthangles are discussed. The implementation of the antenna for creatingthese beams can either be made with separate antenna units or using oneantenna unit giving all the needed beams.

Separate antennas for the two beams can typically be two conventionalantennas with proper polarization directions. The two antennas canmechanically be directed/oriented towards the designed dedicated beamdirections. Alternatively, the two separate antenna units may as well bepositioned within a single enclosure, where the individual antenna uniteither is pre-directed or can be mechanical directed within theenclosure.

In the implementation using one antenna unit (where the same structureis used for both beams), a preferred solution uses an array antenna withbeam-forming means (feed network for example Butler-matrix). In thesimplest form the array have two columns with two polarizationdirections each.

Feeding these two columns with separate but equal beam-forming networkfor each polarization, give common dedicated beam directions for up- anddownlink suitable for all exemplified proposed invention solutions.

Independent of selected antenna implementation, the total beam-form(beam-width, beam-direction, etc.) can be optimized for cell-coverage ofomni-radiating sites, 3-sector sites, 6-sector sites, etc., givingoverall good performance.

Potential performance (capacity/coverage) advantages of two fixed beamsas a TX-div solution are facilitated by enabling simultaneoustransmission for both cell and narrow-beam coverage. This is made in acost efficient way avoiding coherency requirements in the signal pathsof the base station.

In the proposed solution for WCDMA the amount of HW and requirements onthe HW is equal to or lower than the requirements for the existingstandardized conventional TX-div methods. The proposed solution is wellin line to fit the current product development solutions/architecture.

The invention is valid in a solution with several antennas as well asfor a single package antenna.

REFERENCES

-   [1] 3GPP, “Technical Specification 25.214: Physical Layer    Procedures”, www.3gpp.org-   [2] Ulf Forssën et al., “Adaptive Antenna Array for GSM900/DCS1800”,    Proc. 44th Vehicular Technology Conference, Stockholm, June 1994.-   [3] Bo Hagerman and Sara Mazur, “Adaptive Antennas in IS-136    Systems”, Proc. 48th Vehicular Technology Conference, Ottawa, May    1998.-   [4] B. Göransson, B. Hagerman, J. Barta, “Adaptive Antennas in WCDMA    Systems—Link Level Simulation Results Based on typical User    Scenarios”, IEEE VTC 2000 Fall, Boston, Mass., September 2000.-   [5] “Spatial Division Multiple Access Wireless Communication    Systems”, U.S. Pat. No. 5,515,378-   [6] “Microstrip Antenna Array”, Patent application    WO-95/34102/European Patent EP 0 763 264.-   [7] “Directional-beam generative apparatus and associated method”,    U.S. Pat. No. 6,301,238.

1. A method for simultaneously transmitting signals into a cell of acellular system utilizing narrow-beams and non-coherent signal paths,the method comprising: selecting an information signal to a specificuser #k to be transmitted via a dedicated channel; using simultaneouslytwo fixed narrow-beams from a single group of antenna elements having anumber of fixed narrow beams #n, utilizing orthogonal polarization forthe two fixed narrow-beams; dedicating the two fixed narrow-beams asbeam #1 and beam #2; selecting the dedicated channel to be the dedicatedfixed narrow-beam #1 or beam #2 based upon direction/angular/spatialinformation; and producing a broadcast signal transmission from saidsingle group of antenna elements, said broadcast signal transmissiondefining a total cell coverage, the broadcast signal transmissionmatching the coverage of the fixed narrow-beams #n; dividing thebroadcast signal transmission into separate broadcast signal streams,one for each of the two fixed narrow-beams; and wherein the antennaelements of the group which carry the two fixed narrow-beams also carrythe broadcast signal information in separate narrow beams.
 2. The methodaccording to claim 1, further comprising combining the two broadcastsignal streams in combining units with the dedicated combined signalfrom all fixed narrow-beam selected users #n in each of the twobranches.
 3. The method according to claim 1, alternatively combiningdedicated user's signals selected for transmission over a specific fixednarrow-beam #1 or #2 together with an associated broadcast signal streamin a single combiner unit.
 4. The method according to claim 1, furthercomprising utilizing as the two orthogonal polarization states linearpolarization planes slanted at +45° and −45°, respectively.
 5. Anapparatus for simultaneous transmission of signals into a cell andnarrow-beams utilizing non-coherent signal paths characterized in that aselected information signal to a specific user #k is transmitted via adedicated channel; simultaneous two fixed narrow-beams out of a numberof fixed beams #n, utilize orthogonal polarization states for two fixednarrow-beams; the two fixed narrow-beams dedicate a beam #1 and a beam#2; the dedicated channel selected is formed by dedicated fixednarrow-beam #1 or #2 is based upon direction/angular/spatialinformation; a broadcast signal transmission produced defines a totalcell coverage, the broadcast signal transmission matching coverage ofthe fixed narrow-beams #n, the broadcast signal transmission beingdivided into separate broadcast signal streams, one for each of the twofixed narrow-beams; wherein antenna elements which carry the two fixednarrow-beams also carry the broadcast signal transmission in separatenarrow beams.
 6. The apparatus according to claim 5, characterized inthat the broadcast signal transmission is divided into two broadcastsignal streams, one for each of the two fixed narrow-beams.
 7. Theapparatus according to claim 6, characterized in that the two broadcastsignal streams are combined in combining units with the dedicatedcombined signals from all fixed narrow-beam selected users #n in each ofthe two branches.
 8. The apparatus according to claim 6, characterizedin that dedicated user's signals selected for transmission over aspecific fixed narrow-beam #1 or #2 are combined together with anassociated broadcast signal stream in a single combiner unit.
 9. Theapparatus according to claim 5, characterized in that the two orthogonalpolarization states used constitute linear polarization planes slantedat +45° and −45°, respectively.
 10. A transmitter apparatus comprising:a divider for dividing broadcast signal information into a firstbroadcast signal information path and a second broadcast signalinformation path; an antenna group comprising a single group of antennaelements configured to provide a group of narrow beams; a beam selectorconfigured to select from the group of fixed narrow beams, and inaccordance with direction/angular/spatial information for a specificuser, a first narrow beam or a second narrow beam for transmission of aselected information signal to the specific user; a first combinerconfigured to combine the selected information signal with the broadcastsignal information carried on the first broadcast signal informationpath into a first combined signal which is carried by the first narrowbeam; a second combiner configured to combine the selected informationsignal with the broadcast signal information carried on the secondbroadcast signal information path into a second combined signal which iscarried by the second narrow beam; wherein the single antenna group isconfigured to simultaneously transmit the first combined signal carriedby the first narrow beam and the second combined signal carried by thesecond narrow beam utilizing non-coherent signal paths, the first narrowbeam and the second narrow beam having orthogonal polarization states,and wherein the first narrow beam and the second narrow beam are usedboth for dedicated respective fixed narrow lobes and a broadcast lobecovering an entire coverage area of the antenna group; and wherein theantenna elements of the group which carry the first narrow beam and thesecond narrow beam also carry the broadcast signal information.
 11. Theapparatus of claim 10, further comprising a duplex filter configured toobtain the direction/angular/spatial information for the specific useron an uplink transmission received by at least one of the first antennaand the second antenna.
 12. The apparatus of claim 10, furthercomprising a switch which applies the selected information signal toboth the first combiner and the second combiner.
 13. The apparatus ofclaim 10, wherein the two orthogonal polarization states used constitutelinear polarization planes slanted at +45° and −45°, respectively. 14.The apparatus of claim 10, further comprising a single carrier poweramplifier (SCPA) configured to amplify an input: to one of the firstcombiner and the second combiner.
 15. The apparatus of claim 10, furthercomprising a multi-carrier power amplifier (MCPA) configured to amplifyan output to one of the first combiner and the second combiner.
 16. Theapparatus of claim 10, wherein the antenna group comprises a firstantenna element associated with the first narrow beam and a secondantenna element associated with the second narrow beam.
 17. Theapparatus of claim 16, wherein the antenna unit comprises beam formingmeans.
 18. The apparatus of claim 10, wherein the antenna groupcomprises an antenna unit configured to provide both the first narrowbeam and the second narrow beam.
 19. The apparatus of claim 10, whereintransmission of the broadcast signal matches the coverage of the fixednarrow-beams comprising the group of narrow beams.
 20. A method forsimultaneously transmittimg signals into a cell of a cellular systemutilizing narrow-beams, the method comprising: selecting from a group offixed narrow beams, and in accordance with direction/angular/spatialinformation for a specific user, a first narrow beam or a second narrowbeam for transmission of a selected information signal to the specificuser; for a first group of plural users, combining respective pluraldedicated channels into first Combined dedicated signals; for a secondgroup of plural users, combining respective plural dedicated channelsinto second combined dedicated signals; dividing a broadcast signal intoa first broadcast signal stream and a second broadcast signal stream;combining the first broadcast signal stream and the first combineddedicated signals to form a first narrow beam combined signal fortransmission as the first narrow beam by a first antenna element;combining the second broadcast signal stream and the second combineddedicated signals to form a second narrow beam combined signal fortransmission as the second narrow beam by a second antenna element;transmitting the first narrow beam combined signal and the second narrowbeam combined signal with orthogonal polarization with respect to oneanother, the first antenna element and the second antenna elementcomprising a same group of antenna elements; wherein the first combineddedicated signals are carried to the first antenna element by a firstsignal path; wherein the second combined dedicated signals are carriedto the second antenna element by a second signal path; and wherein thefirst signal path and the second signal path are non-coherent.
 21. Atransmitter comprising: a divider configured to divide a broadcastsignal into a first broadcast signal stream and a second broadcastsignal stream; selecting from a group of fixed narrow beams, and inaccordance with direction/angular/spatial information for a specificuser, a first narrow beam or a second narrow beam for transmission of aselected information signal to the specific user; a first combinerconfigured to combine first combined dedicated signals and the firstbroadcast signal stream to form a first narrow beam combined signal, thefirst combined dedicated signals comprising plural dedicated channelsfor a first group of respective plural users; a second combinerconfigured to combine second combined dedicated signals and the secondbroadcast signal stream to form a second narrow beam combined signal,the second combined dedicated signals comprising plural dedicatedchannels for a second group of respective plural users; an antennaelement group comprising a first antenna element and a second antennaelement, the first antenna element being configured to transmit thefirst narrow beam combined signal, the second antenna element beingconfigured to transmit the second narrow beam combined signal withorthogonal polarization with respect to the first narrow beam combinedsignal; and wherein the first antenna element and the second antennaelement which respectively carry the first narrow beam and the secondnarrow beam also carry the broadcast signal information; a first signalpath configured to carry the first combined dedicated signals to thefirst antenna element and a second signal path configured to carry thesecond combined dedicated signals to the second antenna element; andwherein the first signal path and the second signal path arenon-coherent.